The present invention is related generally to the field of wheeled vehicles and more particularly to such wheeled vehicles having a single forward driven wheel and a steerable pair of rear wheels.
For generations, youngsters have enjoyed riding tricycles. However, the advent of low slung molded plastic three-wheeled velocipedes that place the rider behind the front drive wheel rather than above it, has captured much of the standard tricycle market. In fact, the standard form of tricycle is quickly becoming an endangered species and the term "trike" is unknown to many youngsters.
The vehicles that are taking the place of "trikes" are both faster and more maneuverable. One needs only to watch a youngster maneuver his "Big Wheel" (.TM.) into a tight corner at high speed to understand their advantages.
The single most obvious problem with the newer forms of tricycles is that they are designed for youngsters, not for the adolescent to adult group. Adolescents must give up the vehicles they outgrow for the more "grownup" bicycle, leaving behind forever the thrill of scooting along inches from the ground surface.
Another important problem is that the modern "tricycles" are not typically designed to give the rider total control. Bicycles can be leaned into a curve to counteract centrifugal forces. It is primarily the rider rather than mechanical apparatus that initiates and actually produces the turning impetus. On the other hand, the typical tricycle, old or new, is designed with three point ground contact geometry to mechanically withstand such centrifugal forces without substantial assistance from the rider. When the centrifugal force overcomes the resistance produced by the tricycle geometry, the result is an outward slide or roll of the vehicle and rider. The point at which centrifugal outward force overcomes the resistance offered by the tricycle occurs so quickly that it is not generally within the capability of the rider to correct or compensate by shifting his body weight inwardly. It therefore becomes desirable to obtain such a vehicle that provides greater maneuverability than do standard tricycles and that gives the rider greater control over the apparatus in turns.
The maneuverability problem briefly discussed above has been realized to a limited extent by some manufacturers of the new forms of tricycles. Some designs provide rear steering wheels that are set about a fixed inclined steering axis. By doing this, the rider is able to turn the vehicle while simultaneously leaning it in the direction of turn; the sharper the turning radius, the greater the inclination into the turn. These forms of tricycles are an improvement over the fixed wheel variety, but still lack the desirable feature of adjustability for the angle of the steering axis. The rider is therefore still not allowed total vehicular control; steering conditions are the same regardless of the operating speed.